The Institutional Dentist Scientist Training Program of the University of Washington currently supports Douglas S. Ramsay, DMD, in his pursuit of a Ph.D. in experimental psychology. His interests range from the study of anxiety disorders (particularly as related to dental fear) to the effectiveness of drugs used in dental practice. Dr. Ramsay's thesis research is based upon the hypothesis that when drugs cause biological effects, the body responds by activating physiological reflexes or behaviors to restore pre-drug conditions. This hypothesis can be extended to account for drug tolerance. Drug tolerance occurs when a drug causes less effect over repeated usage. The hypothesis is that when a person anticipates receiving a drug(s) he makes a learning response which counters the drug's effects and thereby contributes to tolerance. Therefore, drug tolerance is a function of both what the drug does to the body and, more importantly what body does in response. Dr. Ramsay is applying various predictions of the hypothesis to the study of the pain- and anxiety-relieving properties of nitrous oxide, a drug commonly used in dental practice. His hypothesis is that when nitrous oxide is continuously administered, bodily responses which enhance pain sensitivity may be activated and thereby reduce its analgesic efficacy. For his dissertation, Dr. Ramsay is learning the psychophysics of pain assessment from a collaboration with a group at the Oregon Health Sciences School of Dentistry, and the fundamentals of tolerance and learning theory here at the University of Washington. Ultimately, understanding the body's capability of modulating pain sensitivity may lead to improved methods in the pharmacological management of pain.